Bellows-regulating device



T. MANNBORG BELLOWS REGULATING DEVICE Flled Sept 28, 1925 June 5, 1928.

Patented June 5, 1928.

, UNITED STATES PATENT OFFICE."

THEODOR MANNBORG, OF LEIPZIG-LINDENAU, GERMANY.

BELLOWS-REGULATIN G DEVICE.

Application filed September 28, 1925, Serial No. 59,129, and in Germany'December 8, 1924. I

My invention refers to pneumatic musical instruments in which bellows are provided for supplying the wind for the operation of the instrument. Its particular object is to provide means whereby the wind supply is rendered more uniform than was hitherto the case.

In musical instruments operated by suction wind it is customary to provide a torsional or a V-shaped leaf-spring to act on the suction bellows. It has been found in the operation of these devices that the a plication of such springs involves certain di'awbacks inasmuch as in overcoming the spring pressure exerted on the bellows the resistance offered by the spring increases in proportion as the ends of the spring approach one another. In other words, the resistance offered by the spring during the operation of the bellows is not constant but variable and in consequence thereof the wind is not uniformly produced, so that there arise variations in the strength of the tone.

According to the present inventionthis drawback is obviated by causing the variable spring pressure to be balanced by the pressure of the atmosphere on the surface of the folds of the bellows. This is effected by arranging these folds in such manner that the apex of the angle enclosed by the folding walls of the bellows is disposed on the outside and on the bellows being expanded moves inwards, thus exposing to the atmospheric pressure an increasing effective surface of the folds, whereby the increasing resistance offered by the compressed spring is counterbalanced. Obviously the walls of the folds must be rigid in order to prevent their being deformed by the atmospheric pressure.

In the drawings affixed to this specification and forming part thereof a suction wind device embodying my invention is illustrated diagrammatically by way of example.

In the drawings Figs. 1 and 2 are substantially identical sectional views showing the bellows in closed and opened position, respectively, while Fig. 3 is an end elevation. Referring to the drawings, a is a wind box '12 is the wind admission, 0 is the exhaust. The side wall of box a covered by the bellows is apertured at d. e is the hinge of the movable wall f of the bellows and g are the top foldsof the bellows. As shown in the drawings the apex of the angle enclosed between the folds g of the bellows is directed toward the free atmosphere. it is a spring acting on the movable wall f, one end resting against thiswa'll, while the other end is fixed to the side wall of the box a. Spring h tends to hold the bellows in the normal position shown in Fig. 1. When the device is set operating and the ends of spring happroach each other, the resistance of the spring increases, but simultaneously the folds, which in the normal position shown in Fig. 1 enclose a pointed angle, are unfolded as shown in Fig. 2 where the angle enclosed by them is obtuse. In this position the surface of the folds g which is exposed to the air pressure is considerably larger and in consequence thereof the pressure of the atmospheric air acting thereon is greater, so that the increase in tension of spring it and in the pressure exerted on the movable wall 7 is compensated by the increase in the pressure exerted on the folds air.

to devices of the kind, in whichthe bellows are enclosed in a chamber. I

I wish it to be understood that I do not desire to be limitted to the exact details of construction shown and described for obvito a person ous modifications will occur skilled in the art.

I claim l 7 A bellows regulating, device for pneumatic musical instruments comprising a wind box, a movable wall hinged to said wind box, rigid foldable material inserted between said box and said wall and capable of folding up and expanding, respectively, when said wall is moved, and a spring acting on said movable wall so as to cause the foldable material to fold up, the apex of the angle enclosed between the folds, when folded up, being directed towards the free atmosphere. 7

In testimony whereof I affix my signature.

THEODOR MAN N BORG.

9' by the atmospheric,

Obviously myjinvention is not restricted, 

